“Michael is very aware of Alzheimer’s because we’re surrounded by it,” added his mother, Nancy Clayburgh. “He understands it and understands that his grandfather died from Alzheimer’s and knows he can be involved and help find a cure.”

People with Down syndrome seem to have a double risk: They are more susceptible than the average population to Alzheimer’s disease and struck by it earlier in their lives.

Around 40 percent of people with Down syndrome develop Alzheimer's-like symptoms by age 40 and 50 percent develop symptoms by the age of 50, according to Dr. Brian Skotko, a medical geneticist who is leading the clinical trial at Massachusetts General Hospital.

"Every family that I know that has a person with Down syndrome is well aware of that statistic," said Nancy Clayburgh. "It's a great concern."

The connection between Down syndrome and Alzheimer’s might lie in a gene.

People with Down syndrome are born with an extra copy of chromosome 21.